simjian



Feb. 21, 1956 L. e. SIMJIAN 2,735,231

SHARPENING OR POLISHING DEVICE Filed May 22, 1955 4 MOTOR .5 4 T I u a; REGTIFlER l l l l l l'l l LUTHER G. SIMJIAN INVENTOR.

ATTORNEY United States Patent O 2,735,231 SHARPENING OR POLISHING DEVICE Luther G. Simjian, Greenwich, Conn., assignor to The Reflectone Corporation, Stamford, Conn, a corporation of Connecticut Application May 22, 1953, Serial No. 356,742 11 Claims. (Cl. 51-7) This invention relates to an abrasive bath for polishing or sharpening articles under control of a magnetic field. It has particular reference to an abrasive bath containing magnetic powder which has a consistency which changes as a magnetic field is applied.

As used in the specification and claims the word portion shall define any part of the object which may be in contact with the abrasive mixture.

One of the major difiiculties in resharpening cutting instruments lies in the necessity for accurately adjusting the abrasive to the contour of the cutting edge. For this reason most resharpening is done by hand and the judgement and dexterity of the operator is mainly responsible for the results obtained. A similar problem exists when it is desired to polish or abrade an article which contains an irregular surface, such as a gear, a worm wheel, or other similar articles. The present invention solves these ditficulties by using an abrasive bath for polishing articles and sharpening cutting edges, employing a mixture which consists of an abrasive powder such as carborundum, a magnetic powder such as iron filings, and a liquid which may be any type of lubricating oil. This mixture is housed in a container in which an instrument with a cutting edge is mounted. A variable magnetic field is applied to the mixture in such a manner as to magnetize it for a short time interval and then demagnetize it. This cycle of events is continued until the desired result is obtained. The variation of magnetic force applied to the mixture causes the abrasive particles to move a small distance and thereby cause a polishing action on the surface of an irregular object. 'Other details and variations will be described later.

One of the objects of this invention is to provide an abrasive bath which avoids one or more of the disadvantages and limitations of prior art arrangements.

Another object of the invention is to polish an irregular object without resorting to manual manipulation.

Another object of the invention is to sharpen the edge of a cutting instrument.

Another object of the invention is to polish certain desired surfaces of an irregular object while excluding other surfaces.

One feature of the invention includes a magnetic mixture which is alternately magnetized and demagnetized. During the period when the bath is demagnetized the cutting edge of an instrument is lowered into the bath. During the time the bath is magnetized the instrument is withdrawn from the bath thereby polishing its sides and sharpening its cutting edge.

Another feature of the invention includes a bath containing an abrasive magnetic mixture and means for magnetizing the mixture along certain predetermined paths. After a short time interval the magnetic forces change so as to cause the mixture to be magnetized along other opposite paths, thereby causing the abrasive particles in the bath to realign and shift their position. This action is used to polish the surface of articles immersed in the bath.

For a better understanding of the present invention together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawings.

Fig. l is a cross sectional view of an abrasive bath, showing a magnetic circuit for the bath and means for moving a cutting instrument in the bath.

Fig. 2 is another view, partly in section, similar to Fig. 1 but showing mechanical means for raising and lowering a cutting instrument.

Fig. 3 is a part sectional view of an alternate arrangement using only an alternating current supply to operate both the magnetic field for the bath and to operate a structure for moving the instrument.

' Fig. 4 is a view, partly in cross section showing a polishing bath with a gear positioned therein.

Fig. 5 is a schematic diagram showing two sets of magnets arranged for three phase operation.

Referring now to Fig. 1 a container 10 is employed for retaining a mixture 11 which includes magnetic particles, abrasive particles, and a liquid. A magnetic core 12 is arranged so that its pole pieces project through the container walls and are adjacent to the cutting edge of an instrument 13. This instrument, which may be a surgical knife blade, is secured in a holder 14 which in turn is coupled to an armature 15 which is controlled by an electromagnet 16 having a core 17 and a winding 18. A second winding 20 is positioned around the magnetic core 12 in order to create magnetic flux in the core and the mixture.

Pulsating current for windings 18 and 20 is provided by a rectifier system 21 which is connected to alternating current supply lines 22. Since the circuit for these windings must be broken and closed at definite time intervals a system of two commutators 23 and 24 is provided. The commutators are secured to a shaft 25 which is run by an electric motor 26 connected to supply lines 22. Each commutator has a brush 27 and 28 with which connection is made to the two windings 13 and 20.

The operation of this device is as follows: Let it be assumed at the start that the commutators are turned so that no current flows through either winding 18 or 20. in this condition the knife or instrument 13 is positioned at its lowest point in the bath l1 and the bath has a viscosity which is quite low due to the absence of a magnetic field. Now, if the shafts are turned in a clockwise direction as shown in Fig. 1 current will be first applied to winding 20 through a circuit which may be traced from rectifier 21 over conductor 30 through a brush on shaft 25 to commutator 24, then over brush 28 to winding 20 and back to the rectifier 21 over conductor 31. The magnetism induced in the core 12 causes the bath 11 to become rigid due to the fact that the iron particles in the bathattract each other and form a solid mass with considerable rigidity.

Soon after current is applied to winding 20, current also flows through commutator 23 to brush 27 and through winding 13. This draws the armature 15 up and pulls the cutting edge of instrument 13 in the bath in a direction which is opposite to a cutting motion. As the cutting edge is Withdrawn the attraction of the magnetic particles for each other causes the mixture to close in as the cutting edge is withdrawn. The abrasive particles in the mixture polish the sides of the cutting edge and sharpen it. As shaft 25 continues to revolve insulating portions 32 and 33 will slide under brushes 27 and 28. Current in winding 23* will be cut off first and the mixture will then resume its condition of low viscosity. Then the current in winding 13 is cut oil and the knife blade or instrument 13 again is lowered into the mixture by the action of spring 34. The above described cycle is now repeated for some time and the knife edge on instrument 13 isv sharpened, the speed of such sharpening action depending upon the number of cycles per second, the hardness of the instrument, and the cutting action of the abrasive particles in the mixture.

The abrasive bath shown in Fig. 2 is similar to the one shown in Fig. l and includes a container 19, a mixture 11, a magnetic core 12, and a winding 29. The instrument 13 is secured to a support 14 which in turn is attached to a lever arm which is pivoted at one end on a support 36 and engages a cam 37 with its other end. Cam 37 is secured to shaft 25 on which is mounted a commutator Shaft 25 is turned by a motor 26 and is engaged by a brush 40 which is connected to winding 29. A brush 41 makes contact with commutator 38 and is connected to a source of direct current potential 42, the other end of which is connected to winding 20.

The operation of this device is similar to the device shown in Fig. 1 except that the instrument 13 is raised and lowered by a mechanical cam means instead of a magnet. The results are the same.

Fig. 3 shows an alternate design of the abrasive bath but which employs no commutators nor cams and works directly from an alternating current supply line. The device includes the usual container 10, the abrasive mixture 11, a pair of pole pieces 12, and an instrument 13. Winding 20 is connected to the alternating current supply conductors 22 through a phase changing circuit 43 which includes an inductor 44 and a capacitor 45 either one or both of which may be adjustable. The instrument 13 is secured to a pivoted arm 46which is controlled by a magnet 47. This magnet has a pole piece 48 positioned adjacent to the end of arm 46 which it moves at a frequency equal to the supply frequency on conductors 22.. 'T he action of this device is similar to that of the devices shown in Figs. 1 and 2 except that the motion of the instrument 13 is produced directly by electromagnetic action and the current through winding 20 is produced by the alternating wave delivered by the supply conductors 22.

Fig. 4 illustrates a device for polishing surfaces and comprises a container 10, a bath mixture 11, a magnetic core 12, the pole pieces of which extend into the container It). A winding 20 is connected directly to supply line conductors 22 and provides the core 12 with an. alternating magnetic flux. A gear 50 is mounted within the bath and is secured to a shaft 51 which is rotated by a worm gear assembly 52 and a motor 53. When current is supplied to winding 29 the material in bath 11 will have its viscosity altered in a cyclic manner and the abrasive particles within the mixture will be given a slight vibratory motion, thereby polishing that portion of the gear 56 which lies in the vicinity of the pole pieces of core 12. By slowly rotating the gear all the teeth are brought within the influence of the polishing action and the entire periphery of the gear is polished.

Fig. 5 shows an arrangement for polishing an irregular object which need not be rotated. Two sets of three pole pieces are employed and a switching means 54 is employed to periodically switch from one set of pole pieces to the other. This switching means may be a relay operated device or a commutator mechanism run by a motor. At one interval of time coils 55, 56, and 57 are connected together in three phase relationship with supply lines 58. After a few cycles the switching device 54 switches the current to coils 60, 61, and 62. The pole pieces of one set of coils are mounted in a different plane from the pole pieces of the second set of coils and each set produces a magnetic pattern within the mixture 11 which is different from the pattern produced by the other set. The three phase magnetic flux from either one of the sets of coils produces a vibratory motion of the iron filings within the mixture which is circular in character and therefore pro duces an efficient abrasive action.

it will be apparent to those skilled in the art that the instant device is adapted for polishing any object whose surface to be worked on is either internal or external. The object may be supported from an external means as shown in Figures 1 through 4 or the container and/ or mixture may act as the supporting means as shown in Figure 5.

From the above description it will be evident that an abrasive mixture comprising magnetic particles, abrasive particles, and a liquid can be employed in conjunction with an alternating magnetic field to polish metal surfaces and to sharpen cutting edges.

While there have been described and illustrated specific examples of the invention, it will be obvious that various changes and modifications may be made therein without departing from the field of the invention which should be limited only by the scope of the appended claims.

I claim:

1. A sharpening device for a cutting instrument comprising; a mixture in a container which surrounds a portion of the cutting instrument; said mixture comprising a liquid, abrasive particles, and magnetic particles; means for supporting and moving said portion of said cutting instrument in said mixture; and means applying a variable magnetic field to the mixture to vary the consistency thereof.

2. A sharpening device for a cutting instrument comprising; a mixture in a container which surrounds a portion of the cutting instrument; said mixture comprising a liquid; abrasive particles, and magnetic particles; means 7 for supporting said portion of said cutting instrument in said mixture; means applying a variable magnetic field to the mixture to vary the consistency thereof and means for moving said instrument in a first direction when the consistency of said mixture is decreased and in a second direction when the consistency is increased.

3. A sharpening device as set forth in claim 2 in which said liquid is a non-magnetic fluid.

4. A sharpening device as set forth in claim 2 in which the magnetic particles are iron powder and said fluid is a light oil.

5. A sharpening device for a cutting instrument comprising a mixture in a container which surrounds a portion of the cutting instrument; said mixture comprising a liquid; abrasive particles, and magnetic particles; means for supporting said portion of said instrument in said mixture; electromagnetic means applying a variable magnetic field to the mixture to cyclically vary the consistency of said mixture, and means cyclically moving said instrument in said mixture as the consistency thereof is varied.

6. A sharpening. device for a cutting instrument comprising a mixture in a container which surrounds a portion of the cutting instrument; said mixture comprising a liquid, discrete abrasive particles and discrete magnetic particles; a magnetic core having an electromagnetic winding thereon with pole pieces positioned in proximity to the said portion of said instrument; said magnetic winding connected to a source of electric power with means'for varying the intensity of said power to said winding thereby increasing and decreasing the consistency of said mixture; supporting means for holding said portion of the instrument in said mixture, and means for periodically moving the instrument as the consistency of the mixture is varied.

7. A sharpening device for a cutting instrument as set forth in claim 6 wherein the means for varying the intensity of said power includes a pair of contacts in series with the source and means for closing and opening the contacts.

8. A sharpening device for a cutting instrument as set forth in claim 6 wherein the means for varying the intensity of said power includes a rotary commutator with a brush making contact therewith and power means for rotating said commutator.

9. A sharpening device for a cutting instrument as set forth in claim 6 wherein the means for varying the intensity of said power includes two rotary commutators,

each with a contact brush, one of said brushes connected to the electromagnetic winding and the other of said brushes connected to said electromagnetic means.

10. A device of the character described for polishing the surface of an object comprising; a mixture in a container which surrounds a portion of the object; said mixture comprising a liquid, abrasive particles, and magnetic particles; means for supporting said object in said mixture; and means applying a variable magnetic field to the mixture to vary the consistency thereof.

11. A device of the character described for polishing the surface of an object comprising; a mixture in a container which surrounds a portion of the object; said mixture comprising a liquid, discrete abrasive particles and discrete magnetic particles; a magnetic core having an electromagnetic winding thereon with pole pieces positioned in proximity to the said portion of the object; and

supporting means for holding said object in the mixture.

References Cited in the file of this patent UNITED STATES PATENTS 2,460,918 Bodine Feb. 8, 1949 2,510,675 Baruch June 6, 1950 2,548,373 Hurvitz Apr. 10, 1951 2,554,701 Hackett May 29, 1951 2,616,984 Pare Nov. 4, 1952 FOREIGN PATENTS 485,592 Belgium 1948 722,067 Germany 1942 

